linux-kernel - Re: [PATCH] firmware: dmi: Change size of dmi_ids

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Date: Mon, 29 Apr 2024 14:44:42 +0200
From: Jean Delvare <jdelvare@...e.de>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] firmware: dmi: Change size of dmi_ids_string[] to 256

Hi Tiezhu,

Sorry for the very late answer, somehow your messages slipped through
the cracks.

On Wed, 22 Feb 2023 09:55:01 +0800, Tiezhu Yang wrote:
> The current size of dmi_ids_string[] is 128, the BIOS date
> can not be seen if the total string length of system vendor,
> product name, board name, BIOS version and BIOS date is too
> long to over 128, it is better and enough to change size of
> dmi_ids_string[] to 256 for most cases.

In order to convince me that the size of this buffer needs to be
increased, one would have to provide a real world example with valid
DMI data where the output doesn't fit. However...

> Without this patch:
> 
> [    0.000000] DMI: Loongson Loongson-3A5000-7A1000-1w-A2101/Loongson-LS3A5000-7A1000-1w-A2101, BIOS vUDK2018-LoongArch-V4.0.05132-beta10 12/13/202
> 
> With this patch:
> 
> [    0.000000] DMI: Loongson Loongson-3A5000-7A1000-1w-A2101/Loongson-LS3A5000-7A1000-1w-A2101, BIOS vUDK2018-LoongArch-V4.0.05132-beta10 12/13/2022

This example is apparently taken from an engineering sample with rather
"low quality" strings or invalid string indexes. Specifically:
* The product name and the board name are the exact same string.
* Both duplicate the system vendor name ("Loongson").
* The BIOS version includes the architecture name "LoongArch", which
  seems unnecessarily verbose.

So my feeling is that the issue would be better addressed by fixing the
DMI data of your board than increasing the buffer size.

Do you have any production-grade DMI table with proper strings where
the buffer is still not large enough?

-- 
Jean Delvare
SUSE L3 Support